1. Field of the Invention
The invention concerns an analog radio clock with a receiver and decoder assembly for receiving and decoding a time message transmitted by a time signal transmitter, including an adjustment device by means of which the indicator or display of the radio clock can be adjusted or set to a clock time in accordance with the decoded time message, and including an hour correction device, by means of which the clock time received from the time signal transmitter is adjustable in hourly increments via a manually operated switch assembly, with which an hour correction value is subtracted from the received clock time.
2. Description of the Related Art
This type of radio clock having a time zone conversion possibility has already been known. For example, in DE 42 19 257 A1 a radio clock with an analog indicator mechanism is described. The radio clock is suitable for receiving time messages which are transmitted by a time signal transmitter. For this the radio clock makes use of a receiver and decoder assembly, through which the time message sent by the time signal transmitter can be decoded. In accordance with the decoded clock time, the indicator or display of the analog clock is adjusted. For time zone conversion this known radio clock employs a switch mechanism external of the housing, preferably two push button switches. Upon manipulation of one of the two push button switches, the content of a summation register is increased or decreased. The content of the summation register corresponds to an hour correction value, and the actual content of the hour information of the received time message is increased or decreased in accordance therewith.
For error free time zone selection and programming of the appropriate time zone for the clock time displayed at the moment, the known radio clock has an electro-optic display with cartographic representation of adjacent time zones. The electro-optic display is coupled to the switch for time zone conversion, so that the user of the radio clock can determine without difficulty, to which time zone the instantaneously exhibited time display of the indicator of the radio clock corresponds.
Problems with this type of known radio clock include on the one hand the relatively complex investment of technical resources necessary for the cartographic representation of adjacent time zones through the electro-optic medium. Beyond this the user is not able to determine, in the case of failure of the electro-optic indicator, to which time zone the instantaneously displayed clock time of the display corresponds.
A further problem with this known type of radio clock is comprised therein, that a normally UTC-time transmitting time message transmitter transmits a clock time, which is calibrated to world time that is, Greenwich Mean Time. If the radio clock as known from DE 42 19 257 A1 is employed in the USA, which is obviously intended to be the case since the example shows with the graphic indicator in the figure represents the four time zones of the United States of America, then in that case the push buttons must be exercised four times, in order to display the correct local time in the radio clock. If for example, the radio clock is employed in New York, then in that case as a result of the time displacement of minus 5 hours the push button must be operated 5 times, in order that a hour correction value of minus 5 is entered in the therein provided summation register. Should the owner of the radio clock stop over in San Francisco, then he must operate the push button 8 times, in order that the time displacement of minus 8 hours with respect to UTC-Time is entered in the radio clock. This manipulation is quite inconvenient.
A further problem occurs in this known radio clock when the time signal transmitter transmits as normal the UTC-Time, but at the location of the corresponding time zone however a daylight savings time is in effect. Even when with this known radio clock the correct time zone is entered by using the push buttons, a false display can result for the reason that the hour indicator of the radio clock is not advanced one hour to correspond to the appropriate summer time. If in this case the hour indicator is manipulated in order to set the correct summer time, then the result would be a false time zone indication.
This problem occurs particularly in the USA, since there the time signal sender routinely transmits UTC-Time as the time message and supplements the time message with status bits corresponding to the presence of a summer or winter time period. A direct adjustment of the hour indicator with the transmitted time message is not possible in the United States as a result of the various time zones.
From EP 0 372 432 B1 a further radio clock is known, which is provided with a time zone converter. However, in this case the therein described radio clock is a radio clock with digital indicator. The radio clock is provided with a manually operable hour selector, which provides an hour correction in the hour correction register by repeated operation of a push button or rotation of a rotary knob. The display of the digital radio clock indicates the hour correction value, so that the user of this radio clock knows the number of hours which at any point in time the displayed clock time differs from the clock time of the time signal sender. This radio clock operates on the precondition, that the summer or winter time-change be included directly in the hour information of the time display clock time.
A problem with this type of known radio clock is that these do not automatically adjust themselves to the correct local time when, for example, a battery is placed into the clock. In the case that a battery is installed, the hour correction register is set on the value of zero. As the display, the value transmitted by the time signal sender is simply displayed. The user of the clock must then, on the basis of his own clock, determine whether a deviation exists. In the case that a deviation exits, this time displacement or differential must be entered into the radio clock by means of the hour correction switch.